With the recent development of manufacturing technique of integrated circuits, there has been desired a positive type resist capable of forming a photolithographic pattern having high resolution. In a photolithography method using the positive type resist, the exposed part is removed. Accordingly, the remaining non-exposed part is not modified with light even after the exposed part is removed and, therefore, a pattern can be formed by an additional exposure and development.
As the positive type resist composition, for example, a combination of a compound which generates acids in response to a light irradiation with a polymer having a moiety which is decomposed by attack of generated acids to form an alkali-soluble group has been proposed. For example, Japanese Patent Kokoku No. 2-27660 discloses a combination of a polymer having t-butyl ester groups of carboxylic acids or t-butyl carbonate groups of phenols with a compound which generates an acid in response to a light irradiation. Also, Japanese Patent Kokai No. 3-31845 discloses a combination of a copolymer prepared from a monomer having a t-butyl ester group and another vinyl monomer with an aryl onium salt which generates an acid in response to a light irradiation.
The positive type resist composition ideally can form a good pattern by exposing and developing the non-exposed part again, even after it was once exposed and developed. However, the positive type resist composition actually has poor resolution of pattern after the second exposure and development. Further, the conventional positive type resist composition does not have sufficient adhesion between the resist layer and a substrate and it is inconvenient to treat.